As a conventional linear roller guide device of this type, for example, a guide device shown in FIG. 15 is well known.
Namely, this linear roller guide device has a structure in which a movable block 102 is movably guided along a track rail 100 through a number of rollers 101 disposed to right and left portions of the track rail 100. Two rows of the rollers 101 are disposed to each of the right and left portions of the track rail 100 in vertical direction. As a result, four rows of rollers 101 in total are disposed to the track rail 100. Further, four rows of roller rolling surfaces 103 for rolling the four rows of rollers 101 are formed to the track rail 100 in an entire range in which the movable block 102 is moved.
On the other hand, the movable block 102 is provided with four rows of roller rolling surfaces 104 for clamping the rollers 101 so as to oppose to the roller rolling surfaces 103 formed to the track rail 100. The movable block 102 is also provided with four rows of roller circulating passages 105 in unloaded region for circulating the rollers 101 clamped between the roller rolling surfaces 103;104 from one ends to the other ends of the roller rolling surface 103 of the movable block 102.
These four rows of the rollers 101 are disposed in a form of four rows in total so that a pair of rows of rollers disposed vertically are arranged along each of right and left side surfaces of the track rail 100. These four rows of the rollers 101 have a contacting structure in which a contact angle line S constituted by a line orthogonal to center axes of the rollers 101 disposed in upper two rows is set so as to downwardly incline towards the track rail 100 with an inclination angle of almost 45 with respect to a horizontal line H, while a contact angle line S constituted by a line orthogonal to center axes of the rollers 101 disposed in a pair of lower two rows is set so as to upwardly incline towards the track rail 100 with an inclination angle of almost 45.degree. with respect to a horizontal line H, thus adopting a contacting structure in which the loads applied from every four directions are equally supported by the rollers.
In the linear roller guide device described above, however, there was posed a problem that a high rigidity property inherent in the roller 101 cannot be utilized.
In the case of this linear roller guide device, if deformations to be caused by pre-load or external loads applied to the movable block are not eliminated, a contacting state of the rollers 101 with respect to the roller rolling surfaces 103 and 104 are changed, so that a preferable result excellent in rigid performance cannot be obtained.
Namely, conventionally, the paired upper and lower rows of rollers 101 are arranged along the right and left side surfaces of the track rail 100 so as to be apart from each other in a vertical direction, so that a length L from a base portion of a supporting leg portion 106 of the movable block 102 to the lower roller 101 is made long. As a result, when the preload is applied to the roller 101 or when a load in a horizontal direction is applied to an upper surface of the movable block 102 from the right or left direction as an external load, a moment applied in a direction spreading the supporting leg portion 106 is disadvantageously increased.
Further, when a lifting load (i.e., a load applied in a direction detaching the movable block 102 from the track rail 100) is applied as the external load, a force directing upward is applied to upper surfaces of both right and left end portions of the movable block 102 through screw holes 109 formed at upper surfaces of both right and left end portions of the movable block 102. As a reaction of the upward force, a force directing downward is applied to the roller rolling surfaces 104 of the lower side of the rollers 101. These vertically balancing forces are applied so as to be apart from each other with a lateral distance M between the screw hole 109 and the lower side roller 101, so that a bending moment in a direction for spreading the supporting leg portion 106 will occur.
The bending moment due to this lifting load is caused by separating the screw hole 109 from the lower side roller 101 to each other in a horizontal direction, so that it is ideal to locate the screw hole 109 and the lower side roller 101 at the same position. However, due to exitence of the roller circulating passages 105 in unloaded region, it is difficult to form the screw hole 109 to a central portion of the movable block 102.
With respect to the bending moment to be applied to these supporting leg portions 106, a flexural rigidity at a horizontal portion 107 of the movable block 102 copes with the bending moment. However, when a thickness of the horizontal portion 107 is increased, a height dimension of the movable block 102 will be disadvantageously increased.
Further, conventionally, a skew of the roller 101 has been prevented by retaining both end surfaces of the roller 101 in an axial direction thereof by means of a vertical wall 104a and a roller end surface guide member 108, the vertical wall 104a being provided to one side periphery of the roller rolling surface 104 of the movable block 102 while the roller end surface guide member 108 being provided to the other side periphery of the roller rolling surface 104.
In this regard, the skew is a phenomenon of the roller 101 being rolled in a state where a central axis of the roller 101 is inclined with respect to an axis orthogonal to the rolling direction of the roller 101. When this skew occurs, an excessive stress concentration will occur at the end portion of the roller 101 to thereby cause a deterioration in durability of the roller 101 and the roller rolling surfaces. Therefore, the generation of the skew must be sufficiently prevented.
However, even if the roller end surface guide member 108 is provided as conventionally made, when the movable block 102 per se is deformed as described above, the roller rolling surface 104 is displaced. As a result. thus bringing into the sane result as in the skew generation.
Furthermore, in a conventional art, since the roller end surface guide member 108 for retaining the roller 101 is interposed between the horizontal portion 107 and the upper surface of the track rail 100, a space for installing the roller end surface guide member 108 is required to a portion between the horizontal portion 107 and the upper surface of the track rail 100. As a result, the thickness of the horizontal portion 107 of the movable block 102 is obliged to be decreased and the rigidity thereof cannot be set to a large level.
The present invention has been achieved for solving the problems encountered to the prior art described above, and an object of this invention is to provide a linear roller guide device capable of increasing a structural rigidity of the movable block by improving the arranging relations of the rollers.
Another object of the present invention is to provide a linear roller guide device capable of sufficiently extending a contact length of the roller and sufficiently realizing high-rigidity characteristics of the roller by improving structures of the roller end surface guide portion and the roller retaining portion.